Assuming that ATO (assemble-to-order) supply chain is composed of multiple components suppliers and one manufacturer, who adopts JIT replenishment for some components while the others (Q，r) replenishment, this paper developed a components replenishment model for ATO manufacturer under supply chain management to make a study on its mixed components replenishment policies and the production strategies of suppliers, and presents the qualifications for manufacturer adopting JIT replenishment and the algorithm for optimal strategies of supply chain through theoretical and numerical analysis. We found that the manufacturer should adopt JIT replenishment for those components with higher purchase price, long lead time and high variability of demand to reduce the inventory cost of supply chain and increase its profits.